A gas turbine engine typically includes a compressor section, a combustor, and a turbine section. The compressor section compresses ambient air that enters an inlet. The combustor combines the compressed air with a fuel and ignites the mixture creating combustion products defining a working fluid. The working fluid travels to the turbine section where it is expanded to produce a work output. Within the turbine section are rows of stationary flow directing members comprising vanes directing the working fluid to rows of rotating flow directing members comprising blades coupled to a rotor. Each pair of a row of vanes and a row of blades forms a stage in the turbine section.
Advanced gas turbines with high performance requirements attempt to reduce the aerodynamic losses as much as possible in the turbine section. This in turn results in improvement of the overall thermal efficiency and power output of the engine. Further, it is desirable to reduce hot gas ingestion from a hot gas path into cooled air cavities in the turbine section. Such a reduction of hot gas ingestion results in a smaller cooling air requirement in the cavities, which yields a smaller amount of cooling fluid leakage into the hot gas path, thus further improving the overall thermal efficiency and power output of the engine.